A photonic crystal layer used in a laser element of Patent Literature 1 is configured by periodically burying a plurality of different refractive index regions within a base layer that becomes a base. The laser element includes two-layered photonic crystal layers. Each of the photonic crystal layers has the same patterns periodically arranged, but the patterns are different for each photonic crystal layer.
Patent Literature 2 discloses an example of a technique related to an intensity of linear polarization of a laser beam. According to Patent Literature 2, conventionally, a plurality of circular different refractive index regions has been embedded in the base layer constituting the photonic crystal layer respectively at lattice point positions of a square lattice. In this case, a problem that polarization directions in a plane are not constant has been pointed out. That is, an electric field vector (polarization direction) is generated so as to surround the periphery of each of the different refractive index region, due to performance degradation of a mode, which occurs within the photonic crystal layer. In this regard, Patent Literature 2 discloses a technique in which the performance degradation of the mode is solved by disposing another different refractive index region at an asymmetric position deviated from the square lattice, and it is possible to arrange directions of the electric field vectors as a whole.